Automotive engineers and designers have long sought to create vehicles having aesthetically pleasing exterior and interior designs. Exterior designs have become increasingly uniform over the years. Hence, the importance of uniqueness and aesthetic appeal in the automotive interior has grown. In particular, attractive upholstered coverings for interior trim, seats, and steering wheels are a hallmark of the modern, high-quality automobile. Moreover, ever-higher customer quality demands continue to raise the bar for commercial acceptability, and aesthetic appeal has become paramount in the sale of higher profit margin vehicles. Accordingly, attention has turned to less traditional elements of interior design. One example of such new focus involves the appearance of seams in upholstered interior components such as seats and headrests.
A problem whose resolution has long confounded designers is wrinkling proximate the seam at which adjacent upholstery panels or sheets are joined. This phenomenon has been shown to be particularly acute where the interface of adjacent upholstery sheets involves a curve, for example the ends of headrests, and various other contoured portions of vehicle seats. Because the otherwise flat material must be stretched, compressed or otherwise strained to form a curved shape, buckling, known in the art as “knuckling” tends to occur around seam regions. Thus, an otherwise smoothly curving outer upholstery surface can exhibit unsightly knuckling adjacent the region where the sheets covering the headrest interface. Addressing this phenomenon has also slowed the manufacturing process, which in turn raises manufacturing cost—a highly undesirable effect. It is preferred to have an upholstery sewing process which is simple to perform and reduces sewing time.
Various methods have been developed to address the “knuckling” problem, however, most have met with only limited success. The present invention is directed at least in part to one or more problems or shortcomings set forth above.